• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.10a
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• pp.467-469
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• 2018

Tactical wireless communications often suffer from communication problems such as channel interference and communication disconnection due to the variability of the network topology and poor communication environment. Therefore, it is very important to overcome the problem of communication failure of the wireless communication network caused by the poor tactical environment and to improve the survivability. This paper describes the automatic control methodology of wireless communication equipment to identify and distinguish the situation of communication failure without user intervention and to implement more effective solution.

• Journal of Korea Multimedia Society
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• v.22 no.12
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• pp.1438-1446
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• 2019

Recently, the number of mobile users as well as high-speed Internet user has been increasing rapidly. Moreover, traffic is growing fast as services that provide real-time content such as Youtube and Netflix become popular. The problem of traffic control in real-time content services is important because many people use cell phones to receive real-time content. In this regard, the field of CCN is currently being studied. We studied the mobility of nodes among CCN research fields. Node mobility can be divided into three categories : consumer mobility, intermediate node, and provide mobility. In this paper, we propose Mobility Node Support(MD-INS) to support the intermediate-node mobility in CCN real-time services. Experimental results show that the proposed scheme shows better performance than CCN in terms of service disconnection time and packet loss.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.5
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• pp.209-220
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• 2013

Handover is the technology to minimize data lose of mobile devices and make continuous communication possible even if the device could be moved from one digital cell site to another one. That is, it is a function that enables the mobile user to avoid the disconnection of phone conversations when moving from a specific mobile communication area to another. Today, there are a lot of ongoing researches for fast and efficient hand-over, in order to address phone call's delay and disconnection which are believed to be the mobile network's biggest problems, and these should essentially be resolved in all mobile networks. Thanks to recent technology development in mobile network, the LTE network has been commercialized today and it has finally opened a new era that makes it possible for mobile phones to process data at high speed. In LTE network environment, however, a new authentication key must be generated for the hand-over. In this case, there can be a problem that the authentication process conducted by the hand-over incurs its authentication cost and delay time. This essay suggests an efficient key caching hand-over method which simplifies the authentication process: when UE makes hand-over from oMME to nMME, the oMME keeps the authentication key for a period of time, and if it returns to the previous MME within the key's lifetime, the saved key can be re-used.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.05a
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• pp.43-46
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• 2008

During communication between wireless users, disconnection may occur during the handover process. The high handover latency during the process of handover degrades the service quality of the wireless communications. This problem becomes more crucial if the operation network is transmitting real-time multimedia applications. This paper presents our work on the interworking of protocols in IPv6 mobility management which aims to explore the means to reduce the handover latency. We propose Reducing Handover Latency through Protocols over IPv6 mobility management.

• Journal of Digital Convergence
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• v.10 no.9
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• pp.325-332
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• 2012

VANET(Vehicular Ad-hoc Network), which is a technology to create a network among vehicles, decides the route to the destination using information of neighbors within the transmission range as transmission nodes. The existing routing protocol which uses geographical information can cause delay and disconnection of the network when the density of nodes is not high enough to communicate because it only considers the distance of the relay nodes or destination nodes from the source nodes. To solve the problem, this dissertation suggests a routing algorithm based on zones for stable communications among vehicles in the environment of VANET. I minimize the packet loss rate by dividing the city environment into zones and taking into account not only the distance of the destination but also the density of vehicles to choose the best communications environment. This results in a better performance than the established research when the performance evaluation is implemented.

• Journal of Nutrition and Health
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• v.35 no.8
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• pp.886-895
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• 2002

Introduction and application of virtual education has been rapidly increased in these days. A variation of information communication technology has an effect on education in interconnect with network as internet in the world that exceed the limit of time and regional. Computer and network communication technology through the medium of internet make an entrance cyber education as a new education paradigm. It must be affective on learner who have various educational characteristics and requirements. It begins to appear quality, quantity improvements of knowledge and the development of information technology that web based cyber education. This study was conducted to develop the web based education program and to evaluate the effectiveness of learning satisfaction and accomplishment and to compare the cyber lecture system with the traditional lecture system During the second semester of 2001, this study was investigated 317 registered students in a "Food and Culture" class at Kyungwon University. The data were obtained from pre and post-study with self-administered questionnaire. The evaluation and satisfaction score of students who were registered in cyberclass was negative tendency to compare pre with post-test scores, because of insuffciency of computer-aided lecture system. The major problem was inconvenient in checking system for connecting times in cyberclass which was one of evaluation point in final score. Another problem was frequently disconnection during cyber studying and not to concentrate each time in the cyber lecture because of eye fatigue, boring due to less interesting contents than other newly developed web-site. The students was prefer to mix type of the cyber and traditional lecture type class. The result of final score an each class, the score of cyber class (71.36 $\pm$ 22.44) was significantly lower than other groups (mixed type : 76.66 $\pm$ 19.99, traditional type :79.17 $\pm$ 15.72) (p < 0.05). Cyber class was attempted to present a useful and interesting teaching and learning tool which can be applied successfully in a longer term. The result suggest that various teaching and learning strategies should be developed considering the fact that the student learn alone most in time.t in time.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.57-60
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• 2008

During communication between wireless users, disconnection may occur during the handover process. The high handover latency during the process of handover degrades the service quality of the wireless communications. This problem becomes more crucial if the operation network is transmitting real-time multimedia applications. This paper studies the hanover procedure of mobile IPv6 and investigates various factors affecting the handover latency through mobile IPv6 testbed and evaluates the various parameters for reducing the handover latency.

• Transactions on Electrical and Electronic Materials
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• v.18 no.3
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• pp.169-175
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• 2017

A safe and reliable protection system in distribution networks, specifically, those hosting distribution generation units, needs a robust over-current protection scheme. To avoid unintentional DG disconnection during fault conditions, a protection system should operate quickly and selectively. Therefore, to achieve this aim, satisfying coordination constraints are important for any protection scheme in distribution networks; these pose a challenging task in interconnected and large-scale networks. In this paper, a new coordination strategy, based on the same non-standard time-current curve for all relays, in order to find optimal coordination of directional over-current relays, is proposed. The main aim is to reduce violations, especially miscoordination between pair relays. Besides this, the overall time of operation of relays during primary and backup operations should be minimized concurrently. This work is being tackled based on genetic algorithms and motivated by the heuristic algorithm. For the numerical analysis, to show the superiority of this coordination strategy, the IEEE 30-bus test system, with a mesh structure and supplemented with distributed generation, is put under extensive simulations, and the obtained results are discussed in depth.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.11
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• pp.1961-1965
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• 2008

During communication between wireless users, disconnection may occur during the handover process. The high handover latency during the process of handover degrades the service quality of the wireless communications. This problem becomes more crucial if the operation network is transmitting real-time multimedia applications. This paper studies the hanover procedure of mobile IPv6 and investigates various factors affecting the handover latency through mobile IPv6 testbed and evaluates the various parameters for reducing the handover latency.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.1
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• pp.703-712
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• 2015

This paper proposes the UIGRP, which can tackle the problem of the network disconnection and packet transmission delay caused by turning vehicles frequently in an urban intersection. The UIGRP was designed as follows. First, it calculates the direction of vehicles using the moving direction of vehicles and the location of a destination. Second, it makes the RSU measure the density of an urban intersection. Third, the TGF Algorithm in the UIGRP decides the data transmission paths by setting as an intermediate node, not only the vehicle that is moving in the direction where a destination node is located, but also the node that has the highest density. The TGF algorithm using a moving direction and density minimizes or removes the occurrence of local maximum problems that the existing Greedy Forwarding algorithm has. Therefore, the simulation result shows that UIGRP decreases the occurrence of local maximum problems by 3 and 1 times, and the packet transmission time by 6.12 and 2.04(ms), and increases the success rate of packet transmission by 15 and 3%, compared to the existing GPSR and GPUR.